1. High fidelity distribution of triggered polarization-entangled telecom photons via a 36km intra-city fiber network
- Author
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Strobel, Tim, Kazmaier, Stefan, Bauer, Tobias, Schäfer, Marlon, Choudhary, Ankita, Sharma, Nand Lal, Joos, Raphael, Nawrath, Cornelius, Weber, Jonas H., Nie, Weijie, Bhayani, Ghata, Wagner, Lukas, Bisquerra, André, Geitz, Marc, Braun, Ralf-Peter, Hopfmann, Caspar, Portalupi, Simone L., Becher, Christoph, and Michler, Peter
- Subjects
Quantum Physics ,Physics - Optics - Abstract
Fiber-based distribution of triggered, entangled, single-photon pairs is a key requirement for the future development of terrestrial quantum networks. In this context, semiconductor quantum dots (QDs) are promising candidates for deterministic sources of on-demand polarization-entangled photon pairs. So far, the best QD polarization-entangled-pair sources emit in the near-infrared wavelength regime, where the transmission distance in deployed fibers is limited. Here, to be compatible with existing fiber network infrastructures, bi-directional polarization-conserving quantum frequency conversion (QFC) is employed to convert the QD emission from \unit[780]{nm} to telecom wavelengths. We show the preservation of polarization entanglement after QFC (fidelity to Bell state $F_{\phi^+, conv}=0.972\pm0.003$) of the biexciton transition. As a step towards real-world applicability, high entanglement fidelities ($F_{\phi^+, loop}=0.945\pm0.005$) after the propagation of one photon of the entangled pair along a \unit[35.8]{km} field installed standard single mode fiber link are reported. Furthermore, we successfully demonstrate a second polarization-conversing QFC step back to \unit[780]{nm} preserving entanglement ($F_{\phi^+, back}=0.903\pm0.005$). This further prepares the way for interfacing quantum light to various quantum memories.
- Published
- 2024